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Moon and Companions

February 11, 2012

A couple of close companions help the gibbous Moon light up the sky in the wee hours of tomorrow morning. As they climb into good view around midnight, the star Spica is close to the lower left of the Moon, with the planet Saturn farther to the lower left of Spica. All three will be high in the sky at first light.

Saturn is the brighter of the two companions, and it’s continuing to grow brighter still. By the middle of April, it’ll shine about half again as bright as it is now.

That’s because Earth is catching up to the giant planet. Saturn is the sixth planet out from the Sun — almost 10 times farther out than Earth is. Because it’s so far away, it follows a slow, stately path around the Sun. In fact, that stateliness accounts for the planet’s name; Saturn moves so slowly and regally against the background of stars that it was named for the king of the Titans, the gods who ruled before Zeus and the gods of Olympus.

Because Earth is so much closer to the Sun, it zips along at a much faster pace. It completes almost 30 orbits around the Sun for each orbit that Saturn makes. So about every 12-and-a-half months, Earth overtakes Saturn and passes it by. The two worlds are closest when that happens, so Saturn shines brightest in Earth’s night sky — something that’s coming up in just two months.

For now, look for bright golden Saturn and blue-white Spica keeping company with the Moon in the wee hours of tomorrow morning.


Script by Damond Benningfield, Copyright 2011


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